package com.payment.ktb.view;

import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ListAdapter;
import android.widget.ListView;

/**
 * 自定义挤压头部的listview
 * 
 *
 * 
 */
public class PinnedHeaderListView extends ListView
{

	public interface PinnedHeaderAdapter
	{
		public static final int PINNED_HEADER_GONE = 0;
		public static final int PINNED_HEADER_VISIBLE = 1;
		public static final int PINNED_HEADER_PUSHED_UP = 2;

		int getPinnedHeaderState(int position);

		void configurePinnedHeader(View header, int position, int alpha);
	}

	private static final int MAX_ALPHA = 255;

	private PinnedHeaderAdapter mAdapter;
	private View mHeaderView;
	private boolean mHeaderViewVisible;
	private int mHeaderViewWidth;
	private int mHeaderViewHeight;

	public PinnedHeaderListView(Context context)
	{
		super(context);
	}

	public PinnedHeaderListView(Context context, AttributeSet attrs)
	{
		super(context, attrs);
	}

	public PinnedHeaderListView(Context context, AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);
	}

	protected void onLayout(boolean changed, int left, int top, int right, int bottom)
	{
		super.onLayout(changed, left, top, right, bottom);
		if (mHeaderView != null)
		{
			mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
			configureHeaderView(getFirstVisiblePosition());
		}
	}

	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
	{
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		if (mHeaderView != null)
		{
			measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec);
			mHeaderViewWidth = mHeaderView.getMeasuredWidth();
			mHeaderViewHeight = mHeaderView.getMeasuredHeight();
		}
	}

	public void setPinnedHeaderView(View view)
	{
		mHeaderView = view;
		if (mHeaderView != null)
		{
			setFadingEdgeLength(0);
		}
		requestLayout();
	}

	public void setAdapter(ListAdapter adapter)
	{
		super.setAdapter(adapter);
		mAdapter = (PinnedHeaderAdapter) adapter;
	}

	public void configureHeaderView(int position)
	{
		if (mHeaderView == null)
		{
			return;
		}
		int state = mAdapter.getPinnedHeaderState(position);
		switch (state)
		{
		case PinnedHeaderAdapter.PINNED_HEADER_GONE:
		{


			mHeaderViewVisible = false;
			break;
		}

		case PinnedHeaderAdapter.PINNED_HEADER_VISIBLE:
		{

			mAdapter.configurePinnedHeader(mHeaderView, position, MAX_ALPHA);
			if (mHeaderView.getTop() != 0)
			{
				mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
			}
			mHeaderViewVisible = true;
			break;
		}

		case PinnedHeaderAdapter.PINNED_HEADER_PUSHED_UP:
		{

			View firstView = getChildAt(0);
			int bottom = firstView.getBottom();
			int headerHeight = mHeaderView.getHeight();
			int y;
			int alpha;
			if (bottom < headerHeight)
			{
				y = (bottom - headerHeight);
				alpha = MAX_ALPHA * (headerHeight + y) / headerHeight;
			} else
			{
				y = 0;
				alpha = MAX_ALPHA;
			}


			mAdapter.configurePinnedHeader(mHeaderView, position, alpha);
			if (mHeaderView.getTop() != y)
			{
				mHeaderView.layout(0, y, mHeaderViewWidth, mHeaderViewHeight + y);
			}
			mHeaderViewVisible = true;
			break;
		}
		}
	}

	protected void dispatchDraw(Canvas canvas)
	{
		super.dispatchDraw(canvas);
		if (mHeaderViewVisible)
		{
			drawChild(canvas, mHeaderView, getDrawingTime());
		}
	}
}
